1. Field of the Invention
The present invention relates to an information processing device which acts as a network device search device for searching a device on a network, a control method which is applied to the information processing device, and a program which causes the information processing device to operate.
2. Related Background Art
Conventionally, network devices such as a printer, a multifunctional machine and the like which are connected to a network and can be operated from a computer through the network are generally used. Based on this, various management software which is used to easily use these network devices is developed. Here, it should be noted that the relevant management software provides various functions, for managing the network device, such as the function for searching the device, the function for setting a network address, the device for controlling the device, and the like.
Incidentally, by the management software, there are various systems of searching the device on the network. Here, one of these systems, a so-called broadcast system can be used.
More specifically, in the broadcast system, the management software broadcasts a search request packet for the device through the network, the device which received the search request packet sends a search response to the management software, whereby the presence of the target device is searched. Incidentally, although the relevant broadcast system can be easily implemented, a broadcast packet cannot often pass the router which connects the adjacent networks mutually. This is because a network manager generally sets the router not to execute the routing for the broadcast packet so as to control unnecessary network traffic. As a result, in case of searching the device according to the broadcast system, there is a problem that the searchable range is reluctantly narrowed within an identical subnet.
For this reason, a device search system which uses multicasting instead of the broadcasting is developed. Here, in the multicasting, as well as the broadcasting, it is possible to simultaneously transmit data to plural destinations. However, the multicasting is different from the broadcasting in the point that, by transmitting the data to a specific address dedicated for the multicasting, the relevant data can be transmitted only to a node which prepares data reception from the multicast address. According to such a characteristic of the multicasting, packet routing by the router is often permitted with respect to a multicast packet. Incidentally, it is generally determined according to the following rule whether nor not to transfer the packet received by the router to another network.
FIG. 1 is a diagram showing the constitution of a packet. That is, a TCP/IP (Transmission Control Protocol/Internet Protocol) packet has the constitution as indicated by numeral 101 in FIG. 1, and, in the TCP/IP packet 101, an IP header portion 102 has a TTL (Time To Live) region 103. Although an initial value of the TTL value (i.e., the value of the TTL region) is set to the TTL region 103 by the transmission side, the router which received the TCP/IP packet 101 decreases its TTL value one by one, and then transfers the received packet to another network. At that time, when the TTL value of the received packet is equal to or less than “1”, the router discards the relevant packet without transferring it. By doing so, it is assured that the situation which keeps transferring an unnecessary packet eternally does not occur. According to the above rule, the packet transmission side can control the range that the packet reaches, by appropriately setting the TTL value of the packet that the packet transmission side itself first transmits.
Incidentally, the SLP (Service Location Protocol) defined by the RFC (Request For Comments) 2608 is the protocol which enables to search a service on the network by using the multicasting. FIG. 2 is a diagram showing the packet constitution of the Service Request (function=1) which is the command for searching the service in the SLP, and FIG. 3 is a diagram showing the packet constitution of the Service Reply (function=2) which is the command for causing the service which received the Service Request to transmit a response.
According to the packet constitution as shown in FIG. 2, the transmission side generates the search request packet in which a type 201 and a scope 202 of the service intended to be searched are described, and then transmits the generated search request packet by using the multicasting. Subsequently, the node which received the search request packet on the network analyzes the contents thereof. Here, if it is analyzed that the node conforms to the search condition indicated by the received search request packet, the relevant node transmits the response with the packet constitution shown in FIG. 3. Meanwhile, if it is analyzed that the node does not conform to the search condition, the relevant node discards the received search request packet.
Incidentally, the improvement for controlling (or suppressing) the power consumption in such a network device as above currently advances with the object of energy saving. In particular, in the device such as a printer, a copying machine or the like of which the power consumption is high because it executes image fixation by using heat, it is thought that how power consumption is low contributes to popularize the relevant products including the network device itself. Ordinarily, if the state that the device is not operated or handled by a user for a certain period of time continues, or if the state that communication between the device and another device or a computer is not executed for a certain period of time continues, the relevant device comes to be in a sleep mode (that is, a power saving mode). Then, in the sleep mode, power is fed only to the hardware such as a one-chip microcomputer, a LAN (local area network) controller and the like of which the power consumption is low so as to maintain the bare essentials of the functions. In other words, the relevant device controls the power consumption by stopping unnecessary power feeding. Moreover, the relevant device can restart all the functions in response to a user's operation (or handling). In addition, the relevant device can restart all the functions also when the packet of a specific data format is received from the network. Incidentally, it should be noted that “sleep mode” may be equivalent to “sleep state” throughout the specification and the drawings.
However, since the above network device has the sleep mode as described above, the following problem occurs when the management software searches the device. That is, in the case where the device is in the sleep mode, even if the device search request is transmitted by the management software, no response is returned because the device does not returns to its normal state, whereby it is resultingly impossible to search the device.